The capacity for anaerobic decolorization of a sulfonated azo dye, Congo Red, by a strain of a sulfate-reducing bacterium was evaluated. After optimizing the growth rate of the bacteria on a simple carbon source and terminal electron acceptor pair, lactate and sulfate, respectively, the effect of the dye concentration on their growth rate was analyzed. The decolorization rate was affected by the dye concentration in the growth medium. The azo-bond cleavage mechanism of reductive decolorization with the formation of benzidine was consistent with the results, as this metabolite was identified by high-performance liquid chromatography. Several fractions of the culture medium, including lysed cell extracts, were examined for the capacity to reduce the azo dye. This reduction capacity was found in the culture medium in which the cells had previously grown. The results showed that the mechanism of reductive decolorization of this sulfonated azo dye was extracellular and nonenzymatic, consistent with the production of sulfide anion by the microorganisms while growing on lactate and sulfate. The sulfide anions were the cause of the reduction leading to the disappearance of color in the medium. To increase the rate of decolorization, the presence of ferrous ion was also necessary together with the lactate and sulfate substrates.
Resumo: O presente artigo pretende dar a conhecer os acontecimentos mais relevantes do século XIX relativamente ao ensino da contabilidade . A pesquisa faz uso do método bibliográfico como método de eleição para a recolha de dados, privilegiando o recurso a fontes secundárias de informação, em particular livros, monografias e artigos de periódicos nacionais e internacionais. O texto expõe os principais traços caraterísticos da Aula do Comércio de Lisboa (fundada ainda na centúria de Setecentos), da Aula do Comércio do Porto, do curso de Comércio da Academia Politécnica do Porto, da Escola de Comércio de Lisboa e dos Institutos Industriais e Comerciais de Lisboa e do Porto . Também foi estudado um marco importante da disciplina: a entrada da contabilidade no ensino superior em Portugal .
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